Evaluación estructural probabilística de una cubierta de hormigón suspendida con cables: el Estadio de Braga (Portugal)

Abstract

Cable structures often pose a signi cant challenge, particularly due to the struggle in foreseeing the structural response during the design. Because of this we rely on nite element models, despite their complexity, especially when facing dynamic forces. Hence the need of simpli ed models, optimized to retrace speci c behaviours of the structure and reduce the computational burden. This Master’s degree thesis deals with the case of the Braga Stadium, characterised by a roof of concrete shells supported by suspended cables. The aim is to assess whether reliable results regarding its seismic response can be obtained from simpli ed models. Starting from the provided designs and information, we calculate the cables geometry and performed a static analysis of the cables and the East stand, whose results re exploited to calibrate the simpli ed models. The structural layout on parallel elements allows us to simplify the structure as a planar one: we have assembled three models with increasing amount of simpli cation, that include the cables and the East stand upright. The West stand is not included as on its side the cables are anchored directly to the rock. The models are evaluated through a multi-support analysis, considering the two uttermost cases: with perfectly correlated accelerograms and with uncorrelated accelerograms. We perform several simulations, extrapolating from each one the peak values of the maximum cable force and the maximum relative displacement of its ends. We then processed these data, calculating the main statistical parameters and the empirical distribution functions for each model. [EN] The comparison shows that using simpli ed models we can obtain reliable results for the maximum cable forces, but not for the maximum relative displacements. Furthermore, cable modelling cannot be ignored: any simpli cation must be applied solely to the support structures. Finally, the use of uncorrelated accelerograms causes a signi cant increase of cable forces, even if a realistic scenario would be intermediate to the two considered. This result enhances the need of a multi-support analysis in this kind of structures, especially in case of large span suspended roofs like the one studied here.